There are several things that you can do to make sure that Google does not penalize your site:

Improve the poor quality pages on your website. Ask yourself: is the page useful to my website visitors? If not, improve the content of the page to make it more useful.

It is very likely that the overall user experience is important. Check the usability and the design of your web pages. Your web pages should be easy to navigate and they should have a professional design.

Check the ads/content ratio on your web pages. If a web page mainly consists of ads then it is likely that Google considers it low quality.

There are lots of PDFs available on the web, and you can optimize PDFs to get high-ranking search results. Here are some tips on the right way to do it:

Text Based PDF: Make sure your PDFs are text based.

Properties: Complete the document properties including Title and Meta Data.

Optimization: Optimize the PDF copy as you optimize the web page copy.

Build Links into the PDF: Make sure you include links to your website in your PDFs, and pay attention to the anchor text used. Search engines do recognize these links.

Version: Save PDF in lower version as most of the search engines and visitors won’t have the latest version of Acrobat.

Optimize the file size for search: Using the full version of Acrobat, select Advanced>PDF Optimizer to “right-size” the document. You may also want to enable the “Optimize for Fast Web View” option in the Preferences>General Settings panel. This allows the PDF to be “loaded” a page at a time, rather than waiting for the whole PDF to download.

Placement of PDF File: If you want to use PDFs for high-ranking search results, links to those PDFs should be on web pages closer to the root level of the site’s file structure.

Influence Meta Description for PDFs: While with PDFs you have less control of what is displayed as the description to the search result, you can still influence this. The best way to do this is to make sure that you have a good, optimized sentence or two near the start of your PDF. If these sentences correspond to the search term used, it’s likely that these sentences are the ones that will be displayed as the description under the search result’s heading.

Specify the Reading Stuff: Search engines search the copy of the PDF and select something to display as a description under the search result’s heading. Depending on how the reading order of your PDF is specified, this may lead the search engine to select some pretty strange stuff to display.

There are some important steps you need to take in advance of optimizing the site that can help you quote accurately for the SEO project. Following are the points:

What technology was used to build the site i.e. Flash, PHP, frames, Cold Fusion, JavaScript, Flat HTML etc.?

What is the file extension of the pages i.e. .htm, .php, .cfm etc.?

Does the site contain database driven content? If so, will the URLs contain query strings or does the site use parameter workarounds to remove the query strings?

Are there at least 250 words of text on the home page and other pages to be optimized?

How does the navigation work? Does it use text links or graphical links or JavaScript drop-down menus?

Approximately how many pages does the site contain and how many of these will be optimized?

Does the site have a site map or will it require one?

Does the site have an XML sitemap submitted to Google Sitemaps?

What is the current link popularity of the site?

What is the approximate Google PageRank of the site?

Do you have the ability to edit the source code directly or you need to hand-over the optimized code to programmers for integration?

Do you have permission to alter the visible content of the site?

What are the products/services that the site promotes?

Are the Images already optimized for the targeted keywords?

What are the site's geographical target markets; Are they global, Country specific, State specific or Town specific?

What are the site's demographic target markets; young urban females, working mothers, single parents etc.?

What are the earch keywords or phrases you need to target?

Who are the major competitors online? What are their URLs? What keywords are they targeting?

Do you have access to site traffic logs or statistics to track visitor activity during the campaign?

What are your expectations for the optimization project? Are they realistic?

Answers to the above mentioned questions will determine the complexity of optimization required. This initial analysis will help you to scope the time and costs involved in advance. Getting accurate answers to these questions BEFORE quoting is absolutely crucial. Otherwise you can find yourself in the middle of a project that you have severely under-quoted for.